Low-maintenance coatings

Abstract

The invention provides a substrate bearing a low-maintenance coating. The coating includes two films: a first film comprising silica (e.g., silicon dioxide) and a second film comprising titania (e.g., titanium dioxide). Preferably, both films are provided within particular thickness ranges. The invention also provides methods of depositing such coatings.

1. A low-maintenance coating on a glass sheet, the coating comprising a first film positioned directly over a first major surface of the glass sheet and a second film positioned directly over the first film, wherein the first film includes a base film and has a thickness of less than about 100 angstroms, and wherein the second film includes a photocatalytic film and has a thickness of less than about 100 angstroms. 
     
     
       2. The low-maintenance coating of  claim 1  wherein the base film is silica. 
     
     
       3. The low-maintenance coating of  claim 2  wherein the coated first major surface is in periodic contact with rain. 
     
     
       4. The low-maintenance coating of  claim 1  wherein the photocatalytic film is titania. 
     
     
       5. The low-maintenance coating of  claim 1  wherein the thickness of the first film is between about 70 angstroms and about 100 angstroms. 
     
     
       6. The low-maintenance coating of  claim 1  wherein the thickness of the second film is between about 30 angstroms and about 120 angstroms. 
     
     
       7. The low-maintenance coating of  claim 1  wherein the glass sheet is a window pane mounted in a window frame, and wherein the coated first major surface is exposed to an outdoor environment. 
     
     
       8. The low-maintenance coating of  claim 1  wherein the first film consists essentially of silica and the second film consists essentially of titania. 
     
     
       9. The low-maintenance coating of  claim 8  wherein the silica is silicon dioxide, and the titania is titanium dioxide or substoichiometric titanium oxide. 
     
     
       10. The low-maintenance coating of  claim 1  wherein the first and second films are both sputtered films. 
     
     
       11. A low-maintenance coating on a glass sheet, the coating comprising a first film positioned directly over a first major surface of the glass sheet and a second film positioned directly over the first film, wherein the first film consists essentially of silica and has a thickness of between about 30 angstroms and about 100 angstroms, and wherein the second film consists essentially of titania and has a thickness of less than 100 angstroms but greater than about 30 angstroms. 
     
     
       12. The low-maintenance coating of  claim 11  wherein the second film has a thickness of less than about 80 angstroms.